There really is no issues if it was purchased/obtained before hand. I have mountaineering boots that were purchased before I was vegan, woollen blankets and even some silk sari cloth sleeping bag liners that were all bought before I was even vegetarian. My old hiking boots are on their last legs, but after 30 odd years use, I don't mind. I accept that I knew a lot less about conditions then. They've been well worn, and looked after. I knit with second hand wool, unpicking my old garments and recycling the wool into new. Sometimes, in my view, recycling and looking after the environment around us is just as important. If i didn't continue to make good use of these materials (all purchased before I was vegan), I'd need an alternative and sadly a lot of those alternatives rely on petrochemicals which I'm even less keen on if I'm honest. So using what you have already purchased and getting the best use of of it, actually ensuring it is worn out, repaired, resoled, and worn again before throwing away is, I'm my view, a much better option. But not all vegans will agree. There are some who will tell you you should burn the product to ensure that no one else 'benifits' from that animals death. My view is that given it died before I was vegan (or even vegetarian) ensuring it's death is meaningful is just add important.
Sorry if that sounds like a lecture, it's something I feel very strongly about. Veganism and the environment need to compliment each other not fight against each other. Petrochemical products are not necessarily an improvement. I just don't purchase new (even second hand new) of either.